Lloyd S A, Forsberg A, Wolf-Watz H, Francis M S
Dept of Molecular Biology, Umeå University, S-90187, Umeå, Sweden.
Trends Microbiol. 2001 Aug;9(8):367-71. doi: 10.1016/s0966-842x(01)02100-x.
Many Gram-negative pathogens utilize a type III secretion system (TTSS) to inject toxins into the cytosol of eukaryotic cells. Previous studies have indicated that exported substrates are targeted to the Yersinia TTSS via the coding regions of their 5' mRNA sequences, as well as by their cognate chaperones. However, recent results from our laboratory have challenged the role of mRNA targeting signals, as we have shown that the amino termini of exported substrates are crucial for type III secretion. Here, we discuss the nature of these amino-terminal secretion signals and propose a model for the secretion of exported substrates by amino-terminal and chaperone-mediated signals. In addition, we discuss the roles of chaperones as regulators of virulence gene expression and present models suggesting that such regulation can occur independently of the delivery of their substrates to the secretion apparatus.
许多革兰氏阴性病原体利用III型分泌系统（TTSS）将毒素注入真核细胞的细胞质中。先前的研究表明，输出的底物通过其5'mRNA序列的编码区域及其同源伴侣靶向耶尔森氏菌TTSS。然而，我们实验室最近的结果对mRNA靶向信号的作用提出了质疑，因为我们已经表明输出底物的氨基末端对于III型分泌至关重要。在这里，我们讨论这些氨基末端分泌信号的性质，并提出一个模型，用于通过氨基末端和伴侣介导的信号分泌输出底物。此外，我们讨论了伴侣作为毒力基因表达调节剂的作用，并提出了模型，表明这种调节可以独立于将其底物递送至分泌装置而发生。
